Intracellular Mechanosensation in Intestinal Smooth Muscle: Piezo1 Complexes Amplify Signaling Beyond the Surface.

Area of Science:

• Cellular Biology
• Physiology
• Biophysics

Background:

• Mechanosensation is traditionally attributed to plasma membrane proteins.
• Intestinal smooth muscle contractility is regulated by complex signaling pathways.
• The role of intracellular organelles in mechanotransduction remains largely unexplored.

Purpose of the Study:

• To investigate the existence and function of intracellular mechanosensation in intestinal smooth muscle.
• To identify novel signaling pathways involved in amplifying mechanotransduction.
• To challenge the paradigm that mechanosensation is exclusively a plasma membrane phenomenon.

Main Methods:

• Tissue-level wire myography
• High-resolution confocal microscopy
• Proximity ligation assays
• Patch-clamp electrophysiology on freshly dissociated cells

Main Results:

• Identified a functional intracellular signaling hub originating at the sarcoplasmic reticulum (SR).
• Discovered a nanoscale multiprotein complex (<40 nm) involving intra-Piezo1, Ryanodine Receptor (RyR), and BK_Ca channels.
• Demonstrated that activating this intracellular complex generates BK-mediated outward currents dependent on SR Ca²⁺ stores, confirming organellar mechanotransduction.
• Showed that this complex acts as a molecular brake, reducing smooth muscle contractility and membrane excitability.

Conclusions:

• Mechanotransduction is not confined to the cell surface; intracellular organelles play a crucial role.
• A specialized Sensor-Amplifier-Effector complex involving intra-Piezo1 amplifies cellular sensitivity to physical force.
• This intracellular mechanism provides a critical gain-control system that restrains smooth muscle excitability and regulates gastrointestinal motility.